Hydrocarbon wax deoiling



Patented Aug. 3, 1954 HYDRIOCAR'BON WAX DEOILING Willem JohannesDominicus van Dijck, The Hague, and Willem Martin Mazee, Amsterdam,Netherlands, assignors to Shell Development Company, San Francisco,Calif., a corporation of Delaware No Drawing. Application June 24, 1950,Serial No. 170,250

Claims priority, application Netherlands September 16, 1949 9 Claims. 1

This invention relates to a process for the removal of oil fromoil-containing solid paraflin wax and more particularly it relates to animproved process for the removal of oil from an oil-containing paraiiinwax cake obtained in the solvent dewaxing of a mineral oil, and thesolvent deoiling of oily parafiin wax mixtures.

It is known to the art that a waxy oil including lubricating oildistillate as well as residual fraction can be dewaxed to produce arelatively oil-free wax by adding thereto a relatively nonviscous liquidsolvent which at the dewaxing temperature dissolves the oil and whichsolvent is also substantially a non-solvent for the wax at the waxseparation or dewaxing temperature. Examples of such a solvent aremethyl isobutyl ketone, methyl ethyl ketone, a mixture of methyl ethylketone, benzene and toluene, a mixture of benzene and sulfur dioxide,propane, etc. The resulting admixture after having dissolved the wax andoil therein at an elevated temperature is then cooled to a temperatureat which the wax separates out in a solid state. The precipitated wax isthen separated from the solution by various means such as cold settling,centrifugation or filtration. A Wax cake is thereby produced whichusually contains a substantial proportion of oil dissolved in thesolvent therein. In order to remove the oil from the wax cake it is thepractice to wash the cake with a quantity of a washing liquid which issubstantially a non-solvent for the wax and a solvent for the oil, suchas the solvent used for dewaxing. In practice the washing liquidemployed is the same as the dewaxing solvent and gives a filtratemixture having a viscosity lower than that of the oil alone but greaterthan the dewaxing solvent employed. A double volume of washing liquid isusually used, calculated on the pore volume (interstitial volume) of thewax cake, in order to produce a substantially oil free wax cake.

Another method of dewaxing a waxy oil to produce a relatively oil-freewax is to chill the waxy oil without the addition of a solvent and/ordiluent thereto, to a temperature at which solid wax precipitatestherefrom. The precipitated wax is then separated by various means suchas cold settling, pressing, centrifugation or filtration and theresulting wax cake is washed with a liquid which is substantially anon-solvent for the wax and a solvent for the oil contained in the Waxcake, usually one of the hereinbefore mentioned solvents, to produce arelatively oilfree wax cake. Here also a relatively large volume ofwashing liquid is applied to the wax cake in order to produce anoil-free Wax product; a double amount of washing liquid is usually used,calculated on the pore volume (interstitial volume) of the wax cake.

A principal object of the present invention is to provide an improvedprocess of rapidly and efficiently producing by washing an oil-free waxfrom an oil-containing wax cake. A further object is to provide animproved process for the production of an oil-free parafiin wax from awaxy oil or an oily wax mixture.

Now in accordance with this invention it has been found that these andother objects are achieved by washing an oil-containing wax with awashing liquid which at the washing temperature is more viscous than thethe oil-containing liquid which is present in the wax. Moreparticularly, it has been found that in a process of producing anoil-free wax wherein oil-containing wax is washed with a washing liquidwhich is a solvent for the oil and a non-solvent for the wax, especiallyeffective results are obtained when the washing liquid is between about1.5 and about 6 times as viscous as the oil-containing liquid in theWax.

The invention is particularly applicable to the preparation of oil-freewax from wax obtained in the solvent dewaxing of a waxy mineral oil.

In the solvent dewaxing of mineral oil, afterv precipitation andseparation of the wax, a wax cake is obtained usually containing aconsiderable amount of oil dissolved in the solvent present therein. Itis normal practice in order to produce an oil-free wax therefrom toremove the oil from the wax cake by washing the wax cake with anadditional amount of the same solvent employed in the solvent dewaxingstep. Accordingly, if methyl isobutyl ketone were employed as thedewaxing solvent, methyl isobutyl ketone would also be used asthewashing liquid. In accordance with the present invention, however, ithas been found to be advantageous to employ as the washing liquid asolvent which differs from the solvent employed in the dewaxing step andwhich is more viscous at the washing temperature than the first useddewaxing solvent, preferably having a viscosity which is between about1.5 and 6 times the viscosity of the oilcontaining liquid present in thewax to be washed.

When applying this method in practice since the washing liquid as wellas the dewaxing solvent is desirably recovered and recycled after use,it is advantageous to select a washing liquid which can easily beseparated from the oil and from the dewaxing solvent. For example, it ispreferable that the boiling point of the washin liquid difiersuficiently from the boiling points of the oil and of the dewaxingsolvent so that these materials may be readily separated from each otherby distillation. Washing liquids which possess suitable boiling points(the choice of which depends upon the viscosity of the oilcontainingliquid in the wax cake in accordance with the invention) for the methodof the invention comprise liquid aromatic amines such as methyl aniline,ethyl aniline, diethyl aniline; certain aliphatic alcohols such aspropyl alcohol, iso-propyl alcohol, n-butyl alcohol; cyclic alcoholssuch as cyclohexanol; certain halogenated hydrocarbons such astetrachloroethane, etc. Moreover, it is pointed out that the process ofthe invention is particularly adapted to those washing operations of thetype wherein the liquid to be removed from the solid (Wax) is displacedby a washing liquid, e. g., filter cake washing or washing carried outin a centrifuge, rather than a dilution type washing, e. g., preparationof a wax-washing liquid slurry and followed by filtration.

The process of the invention and the advantages to be obtained therefromwill be further elucidated with reference to the following examples ofthe invention.

EXAMPLE I One volume of a Tandjoeng mineral oil distillate fractionhaving a boiling point range 430- 437 C. at atm. pressure containingabout 60% by weight parafin wax was mixed with five (5) volumes ofmethyl isobutyl ketone and the resulting mixture was cooled to C. Theparaffin wax which separated therefrom as a solid was removed byfiltration and had a melting point of 64 C., and a refractive index of70 C. of 1.4348 (D line). The filtrate obtained consisted of oildissolved in methyl isobutyl ketone and had a viscosity of 0.9centipoise at 10 C., the dewaxing and filtering temperature.

Wax cake obtained in the above manner was washed at a temperature of 10C. with the following various washing liquids, cyclohexanol (viscosity124 cps. at 10 C.) n-butanol (viscosity 4.8 cps. at 10 0.),tetrachloro-ethane (viscosity 1.4 cps. at 10 C.) and methyl isobutylketone viscosity 0.83 cp. at 10 0.).

The amount of oil remaining in the wax cake was determined after eachwashing for the varying volumes of washing liquid (expressed as per centof pore volume of the wax cake) and for the various washing liquidsemployed. The experiments were carried out employing three diilerentamounts of washing liquid, namely, 94%, 100% and 120% by volume of thepore volume. The results obtained are presented in Table I.

Table I SOLVENT WASHING 0F OILY WAX CAKE Volume Percent of WashingLiquid Washing Liquid C-yclo-liexauol (124 cps.) percent oll n-butanol(4.8 cps.) do tetrachloro-ethaue (1.4 cps.) .do methyl isobutyl ketone(0.83 cp.) cdo.

The above results demonstrate that by using a washing liquid which,according to the invention, is more viscous than the oil-containingliquid present in the wax cake (viscosity 0.9 cp. at 10 C.) the oilpresent in the wax cake is removed much more satisfactorily andconsiderably less washing liquid is required (depending upon theviscosity of the washing liquid) than if the dewaxing solvent, itself(methyl isobutyl ketone), which has a lower viscosity than theoil-containing liquid in the wax cake, was employed as the washingliquid. Furthermore, the above results demonstrate that the greater theviscosity of the washing liquid over the oil-containing liquid presentin the wax cake, the more thoroughly and efficiently the washing (oilremoval) is accomplished and a smaller quantity of washing liquid isrequired to give an oil-free wax. As a practical consideration, however,the viscosity of the washing liquid should not be too great otherwisethe rate of filtration would be too low. For this reason it is preferredthat the viscosity of the washing liquid should be between about 1.5 andabout 6 times greater than the viscosity of the oil-containing liquid inthe wax cake.

EXAMPLE II Experiments similar to those described in Example I but at adewaxing temperature of l0 C. were carried out upon a Concepcion mineraloil distillate fraction having a wide boiling point range, a specificgravity of 0.879, a viscosity at 70 C. of 3.9 degrees Engler andcontaining about 20% by weight paraffin wax. The parafiin wax whichseparated therefrom as a solid was removed by filtration. The filtrateobtained consisted of oil dissolved in methyl isobutyl ketone and had aviscosity of 2.3 cps. at l0 C., the dewaxing and filtering temperature.

Wax cake obtained in the above manner was washed at a temperature of -l0C. with the following various washing liquids: n-butanol (viscosity 8.4cps. at 10 C.) and methyl isobutyl ketone (viscosity 1.1 cps. at l0 C.).The percentage oil remaining in the wax cake was determined after eachwashing for each solvent. The results are presented in Table II.

Table II n-butanol (8.4 cps.) percent 0il methyl isobutyl ketoue (1.1cps.) do.

The washing liquid employed according to the invention may consist of amixture of liquids, e. g. a mixture of the dewaxing solvent and aviscosity-enhancing liquid such as a glycol.

When using e. g. methyl ethyl ketone as the dewaxing solvent (viscosity0.5 cp. at 0 C.) the addition of 20% ethylene glycol raises theviscosity to 1.5 cps. at 0 C. and the addition of 40% ethylene glycol to3.5 cps. at 0 C. The liquid mixtures thus obtained may be used aswashing liquid.

When a mixture of liquids is used as the washing liquid the mixtureshould of course be a solvent for the oil and substantially anon-solvent for the wax.

The washing liquid may to advantage be substantially saturated with waxin order to prevent its dissolving wax from the cake to be washed.

If a substantial amount of wax would be dissolved from the cake, thelarger pores, through which proportionally the greater part of thesolvent will pass, would be still more enlarged and the inhomogeneity ofthe liquid flow would aggravate.

We claim as our invention:

1. The process of producing a substantially oil-free wax from awax-containing mineral oil which comprises: forming a solution of saidmineral oil with a first liquid consisting essentially of a ketonedewaxing solvent; cooling said solution to a temperature sufl'icient toprecipitate solid wax; separating therefrom solid wax containing anoil-containing liquid comprising said first liquid dewaxing solventtogether with oil dissolved therein; washing said separated solid waxwith a second liquid characterized by having an absolute viscosity atthe temperature of contacting at least 1.5 times greater than theabsolute viscosity of said oil-containing liquid and furthercharacterized by being a solvent for oil and substantially a non-solventfor wax at the temperature of contacting, the washing being eifectedunder conditions to prevent the dissolving of substantial amounts ofsolid wax in said second liquid, and recovering a solid waxsubstantially free of said oil-containing liquid.

2. The process according to claim 1 wherein the second liquid has anabsolute viscosity between about 1.5 and about 6 times greater than theabsolute viscosity of the oil-containing liquid.

3. The process according to claim 1 wherein the second liquid consistsessentially of an alcohol.

4. The process according to claim 3 wherein the second liquid is amixture of a ketone and ethylene glycol.

5. The process according to claim 3 wherein the second liquid has anabsolute viscosity between about 1.5 and about 6 times greater than theabsolute viscosity of the oil-containing liquid.

6. The process of producing a substantially oil-free wax from aWax-containing mineral oil which comprises: forming a solution of saidmineral oil with methyl isobutyl ketone; cooling said solution to atemperature sufiicient to precipitate solid wax; separating therefromsolid wax containing an oil-containing liquid comprising methyl isobutylketone together with oil dissolved therein; washing said separated solidwax with n-butanol and recovering a solid wax substantially free of saidoil-containing liquid.

7. The process of producing a substantially oil-free wax from awax-containing mineral oil which comprises: forming a solution of saidmineral oil with methyl isobutyl ketone; cooling said solution to atemperature sufiicient to precipitate solid wax; separating therefromsolid w containing an oil-containing liquid comprising methyl isobutylketone together with oil dissolved therein; washing said separated solidwax with tetrachloroethane and recovering a solid wax substantially freeof said oil-containing liquid.

8. The process of producing a substantially oil-free Wax from awax-containing mineral oil which comprises: forming a solution of saidmineral oil with methyl isobutyl ketone; cooling said solution to atemperature sufficient to precipitate solid wax; separating therefromsolid wax containing an oil-containing liquid comprising methyl isobutylketone together with oil dissolved therein; washing said separated solidwax with cyclohexanol and recovering a solid wax substantially free ofsaid oil-containing liquid.

9. The process of producing a substantially oil-free wax from awax-containing mineral oil which comprises forming a solution of saidmineral oil with a first liquid consisting essentially of a ketonedewaxing solvent; cooling said solution to a temperature sufiicient toprecipitate solid wax; separating therefrom solid wax containing anoil-containing liquid comprising said first liquid dewaxing solventtogether with oil dissolved therein; washing said separated solid waxwith a second liquid substantially saturated with wax, said secondliquid being characterized by having an absolute viscosity at thetemperature of contacting at least 1.5 times greater than the absoluteviscosity of said oil-containing liquid and further characterized bybeing a solvent for oil and substantially a non-solvent for wax at thetemperature of washing, the washing being efiected under conditions toprevent the dissolving of substantial amounts of solid wax in saidsecond liquid, and recovering a solid wax substantially free of saidoil-containing liquid.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,848,636 Livingstone Mar. 8, 1932 2,048,513 Page July 21,1936 2,229,659 Carr Jan. 28, 1941 2,592,490 Thompson Apr. 8, 19522,595,468 Kiersted, Jr. et a1. May 6, 1952 OTHER REFERENCES Lange,Handbook of Chemistry, Sixth edition, Sept. 1946, pages 1571-1576.Published by Handbook Publishers Inc., Sandusky, Ohio.

1. THE PROCESS OF PRODUCING A SUBSTANTIALLY OIL-FREE WAX FROM AWAX-CONTAINING MINERAL OIL WHICH COMPRISES: FORMING A SOLUTION OF SAIDMINERAL OIL WITH A FIRST LIQUID CONSISTING ESSENTIALLY OF A KETONEDEWAXING SOLVENT; COOLING SAID SOLUTION TO A TEMPERATURE SUFFICIENT TOPRECIPITATE SOLID WAX; SEPARATING THEREFROM SOLID WAX CONTAINING ANOIL-CONTAINING LIQUID COMPRISING SAID FIRST LIQUID DEWAXING SOLVENTTOGETHER WITH OIL DISSOLVD THEREIN; WASHING SAID SEPARATED SOLID WAXWITH A SECOND LIQUID CHARACTERIZED BY HAVING AN ABSOLUTE VISCOSITY ATTHE TEMPERATURE OF CONTACTING AT LEAST 1.5 TIMES GREATER THAN THEABSOLUTE VISCOSITY OF SAID OIL-CONTAINING LIQUID AND FURTHERCHARACTERIZED BY BEING A SOLVENT FOR OIL AND SUBSTANTIALLY A NON-SOLVENTFOR WAX AT THE TEMPERATURE OF CONTACTING, THE WASHING BEING EFFECTEDUNDER CONDITIONS TO PREVENT THE DISSOLVING OF SUBSTANTIAL AMOUNTS OFSOLID WAX IN SAID SECOND LIQUID, AND RECOVERING A SOLID WAXSUBSTANTIALLY FREE OF SAID OIL-CONTAINING LIQUID.